Asked today if he’d agree to be Mitt Romney’s running mate, Chris Christie said, "He might be able to convince me, he's a convincing guy." Romney had better hope he can convince Christie, because he desperately needs the New Jersey governor to balance his ticket.

That may sound like an odd statement. Christie, like Romney, is a moderate governor from the northeast with no foreign policy experience. He’s also a white man. But Christie brings balance where it counts—he has the political and legislative strengths to back Romney up where he is weakest, both in the campaign and in the presidency.

Strength #1: Christie Can Sell Moderation to Conservatives

It’s widely assumed that Romney needs a rock-ribbed conservative to reassure base voters that his "Massachusetts Moderate" days are over. But that poses risks in the center: Romney could be left, for example, defending Marco Rubio’s vote against both versions of the Violence Against Women Act. And there’s no guarantee that the base would view such a pick as anything but a pander.

What Romney really needs is a running mate who can get conservatives excited about electing a moderate candidate. And Christie has managed to become a rockstar among conservatives nationally while pursuing an agenda that is in many ways moderate.

While Christie’s first budget included significant cuts to many programs, it also expanded food stamp eligibility to families making up to 185 percent of the federal poverty line, from a previous level of 130 percent. His administration has made treatment for low-level drug offenders and the reintegration of ex-convicts into the job market a priority. He nominated the first openly gay man to the state supreme court and vociferously defended a Muslim lower court nominee who came under attack from conservatives. (Asked about fears over Sharia Law, Christie said, “This Sharia Law business is crap!”) He has criticized both political parties in Washington for excessive obstinacy.

So why does Christie sell so well with conservatives? Partly, it’s because his agenda also includes conservative initiatives they’re wild about. He has been a strong proponent of education reform. He got a somewhat aggressive pension and health benefits reform through a legislature controlled by Democrats, saving hundreds of millions of dollars a year. And he has fought to cut taxes in the most heavily taxed state in the country, even going around the state to campaign against local budget proposals he deemed too spendy.

But just as importantly, Christie drives liberals insane. By picking constant fights with teachers’ unions and other conservative bugbears, Christie signals to the base that he’s on their side, and they instinctively line up with him. They like his style enough that they are willing to be flexible on the substance.

Putting Christie on the ticket would therefore give Romney the best of both worlds: increased credibility with conservatives without actually having to take policy stances that alienate moderates. A recent poll shows how that formula is working: Christie’s approval in New Jersey stands at 92 percent among Republicans, but he’s also picking up 64 percent of independents and even 30 percent of Democrats.